Abstract

We report for the first time that an ultra-thin hybrid metamaterial slab can reflect an incident plane wave in −1st diffraction order, giving rise to anomalous reflection in a “negative” way. The functionality is derived from the hybridized surface resonant states of the slab. The retro-directive reflection is demonstrated numerically for a Gaussian beam at oblique incidence and verified experimentally at microwave frequencies.

The transverse electric (TE) polarized incident wave with the electric field E//x is blind to the air gaps between the metallic strips`, and treats the whole structure as a homogeneous dielectric slab with PEC ground effectively.

The transverse electric (TE) polarized incident wave with the electric field E//x is blind to the air gaps between the metallic strips`, and treats the whole structure as a homogeneous dielectric slab with PEC ground effectively.

Figures (4)

(a) Schematic configuration of the hybrid slab. The regions containing perfectly electric conductor (PEC) or dielectric are marked by orange color or blue color. The geometrical parameters are a=20mm,b=6mm,g=1mm,h=1.6mmand t=0.035mm. The permittivity of dielectric slab isεr=2.65. A transverse magnetic (TM) plane wave is incident in y^z^plane with an incident angle θ, the magnetic field is along the y axis. (b) The functionality of the hybrid slab can be understood as the result of the coupling of a chain of alternating cavities A and B.

Reflectivity spectra of the0th(red solid lines) −1st (blue dashed lines) and + 1st(dark yellow short-dashed lines) order of reflected waves for TM polarized incident plane waves with different incident angles θ=0°,10°,20°and 30°. The frequencies in white regions [(b)-(d)] confirm that only 0th and −1st reflected waves propagate in the free space with real wave vector component along z axis. The colored arrows in the inset of (a) schematically illustrate the directions of the incidence I0 (black) and the corresponding reflected waves in the 0th order (red), the −1st order (blue), and the + 1st order (dark yellow).

(a) Dispersion diagram of surface resonance states on the hybrid slab. Reflectivity of the 0th or -1st reflected diffractive waves matching to theky≥0orky<0 surface resonances on branch B4 and B5 in colored region of reciprocal space are marked with the size of the symbol being proportional the magnitude of the reflectivity (see text for details). The reflectivity is also plotted as a function of incident angles at (b) for f=7.65GHz, (c) forf=9.88GHz and (d) forf=10.88GHz.

Negative reflection from the hybrid slab at 7.65GHz with an incident angle atθ=44.6°. FDTD simulations with one-way Gaussian beam incident on (a) a PEC slab, and (b) a hybrid slab. (c) The angular spectra of the measured reflection intensity in far-field. (d) Snapshot of local field patterns inside the rectangle box illustrated in Fig. 4(b). The insets in (a) and (b) illustrate the structure of PEC slab and hybrid slab. The positions of one-way Gaussian beam are indicated by horizontal thin lines in (a) and (b). Black arrows refers to the directions of incident Gaussian beams, while red and blue arrows refer to the directions of specular reflection from PEC slab and that of negative reflection from hybrid slab respectively.